It is more than a month since Russian forces said they had fully surrounded the Chechen capital, Grozny, warning those inside the city to get out or face a deadly assault from the air.

Thousands of bombs, shells and rockets later they have apparently made little advance inside the city.

Russian units have probed deep towards the city centre, but have not established positions there.

Occasionally these operations have resulted in disaster, as on 15 December when a reconnaissance column came under fire in the Minutka district, resulting in the loss of dozens of men and at least seven armoured vehicles.

Outside Grozny, Russian progress has also been painfully slow - at least since the early hours of the invasion when the northern third of the breakaway republic was occupied in just four days.

Rebel counter-attacks

The latest counter-attacks in the three biggest population centres outside Grozny - Gudermes, Argun and Shali - show how shaky the Russian presence is in cities they have claim to control.

Russian progress has been slow outside Grozny

Last week, the rebels launched daring raids on three villages to the southwest of Grozny, in which they claimed to have destroyed the headquarters of the then commander of the western front, General Vladimir Shamanov.

And back in November, during their first counter-attack of the current campaign, the rebels briefly recaptured the town of Novogroznensky.

Bunkers

The Russian advance was never expected to sweep across all areas of Chechnya with equal ease. The north is flat, and ideally suited to the Russians' heavy armour. The population is also traditionally less militant than in the south of the country.

It was clear that Moscow would need to exercise caution inside Grozny - where its forces suffered disastrous losses in the last war - and that any advance up the winding valleys and gorges of Chechnya's southern mountains would be laborious.

But the events of the last week highlight another problem for the Russian forces.

Their strategy for minimising casualties, as they have explained many times, is to rely as far as possible on aerial bombardment.

Russian officials search suspected militants in Shali

But the Chechen guerrillas have shown that they can withstand this bombardment and emerge from their bunkers to fight Russian ground troops with deadly efficiency.

The Russian strategy therefore appears to be a recipe for stalemate, and one that plays into the hands of the mobile guerrillas.

Their ploy has been the same whenever they have fought the Russians over the last two centuries - repeatedly strike and withdraw.

Disguise

In Grozny they can move around in sewers and trenches, and in the mountains they have the cover of beech forests.

Russian soldiers are hampered because they have trouble distinguishing ordinary civilians from rebel fighters. Recently, generals complained that a counter-attack had been carried out by men who had pretended to be refugees.

In the last war the Chechens often fought in shifts, so that a man who was a civilian one day would become a fighter the next before going home again to recuperate.

Chechen leaders have often remarked that the Russian army can control only the ground under its feet, and that the rest of the country belongs to them.

There is some truth in this claim, as the recent burning down of a Russian field hospital in the town of Chervlennaya demonstrates. The town, 15 miles north of Grozny, has been in Russian hands since the first days of the conflict, but still it is not immune from sabotage.

Unwinnable war

From the start of this conflict, many military experts have predicted another protracted and ultimately unwinnable guerrilla war.

This is all the more likely to be the case as long as Russian forces shrink from close-quarters combat with Chechens.

It may be that Russia is now preparing for a change of tactics, having replaced the two commanders that have led the eastern and western fronts to date.

One of the new commanders, General Sergei Makarov, has said his forces had been given new "more complicated" instructions.

However, if this means putting less reliance on long-distance methods of warfare, the Russian casualty rate, already rising, is likely to continue to increase.